Traffic control system



Jan. 11, 1938. A. P. B. RENS HAW 2,105,443

TRAFFIC CONTROL SYSTEM Filed Jan. 19, 1955 s Sheets-Sheet 1 /0 l H/ 0 XF/P :9

IN VEN TOR ALF/9.50 PERCY 54/1 Pf/Vfi/MW dwwwfi, 18mm FM A TTORNEYS Jan. 11, 193$. P, REN HAW 2,105,443

TRAFFIC CONTROL SYSTEM oia/M/d, 6mm, 9%

A TTORNE Y5 Jan. 11, 1938. A. P. B. RENSHAW ,4 3

TRAFFI C CONTROL SYSTEM Filed Jan. 19, 1935 s Sheets-sheaf, 5

IN VENTOR A1 F260 P5907 fiA/Lsy PtWSf/AW BY A TTORNEYS Patented Jan. 11, 1938 UNITED," STATES groans mm common sYs'rEM Alfred Percy Bailey Renshaw, Kingston Hill, England, assignor, by mesne assignments, to Automatic Telephone & Electric Company,

Limited, London, England Application January 19, 1935, Serial No. 2,480 In Great Britain February 5, 1934 I 18 Claims.

The present invention relates 'to traflic control systems foruse at the intersection of interferrlng traflic lanes and is more particularly concerned with a progressive type traific control system by 5 means of which a number of controllers located at adjacent intersections on a main road may.

be regulated from a master controller in a definite phase relationship to another. In known forms of progressive systems it has been found that for eiiicient working the value of the cycle controllers at the time requires alteration a number of times each day to cater for diiferent conditions of traffic,-

and various methods have been employed to overcome this difliculty such as manually or clockcontrolledcycle adjustment.

The principal object of the present invention generally stated is to provide an improved progressive traffic control system in which the cycle time is variable automatically in accordance with the trafiic conditionsexisting at any particular time.

More specifically, one object of the invention is to provide a traflic control system for a plurality of intersections in several intersections are operated on a cycle of variable length depending upon the cycle length of a controller at one intersection which is selected as having typical'trafiic conditions, and which is equipped with vehicle de-'- tectors in the several lanes of approach thereto.

In applying the principles of the invention the area to be controlled is first surveyed as regards its tramc conditions to locate what will be known as the key intersections, that is, in eifect sample intersections or intersections at which the conditionsmaybe considered as typical of those existing at the intersections in the immediate vicinity. ,When the key intersections have been selected, the remaining intersections to be controlled are shared out between them with the result that the area is split up into a number of groups, eachcontaining a key intersection "and half a dozen or so dependent intersections which are assumed to have similar traific conditions and are controlled from the key intersection of the group. In each group the key intersection is provided with a key controller-and a master timer, construction of which will subsequently appear. .and vehicle actuatableflevices, or detectors,

-in'each of its several lanes of approach. The dependent intersections of each group are equipped with controllers which may be regu-' lated from the master timer of that group in a desired phase relationship with one another. and which may be called dependent controllers.

which the right of way signal In one aspect of the invention the arrangement for adjusting the time cycle of the master timer by the key controller to more nearly conform to the cycle of the latter has general application in the field of synchronizing a. secondary 5 at the end of the master timer cycle so that its following cycle will be shorter. If on the other hand the master timer finishes its cycle first, an adjustment will be made to increase the length of its following cycle. In-each case the adjustment will not be sufiicient to correct the master timer cycle completely unless the discrepancy is very small otherwise the cycle would vary as at a fully vehicle-actuated intersection,

and a progressive flexible system would be impossible. Small adjustments therefore, onlyare made and the master timer cycle value becomes an average of the cycle time of the key controller. If the key controller finishes its cycle before the master timer, it waits until the master timer has finished its cycle, and it is clearly desirable that the controller shall be connected so that at the end of the cycle right of way is with the main road. If the key controller finishes its cycle after the master timer after possibly some degree of curtailment, it will immediately start its next cycle, but the master timer itself does not stop under any conditions. By this means the dependent controllers can be linked to form a progressive system which is governed by a cycle time varying ,on the average with that at the key point.

come under the control of the master timer. It

is also. possible within a particular group to employ different types of dependent controllers so as to form a combination of two or more of the three types described.

The invention will be better understood from the following description of one method of carrying it into effect which may advantageously utilize arrangements disclosed in British specification 403,732, from which specification portions describing these arrangements are reproduced herein. Application Serial Number 677,029, filed June 22, 1933 under the international convention, corresponds with British specification 403,732 and is now co-pending with the present application. No claim is made in the present application to subject matter common to the present application and the co-pending application, such subject matter being claimed in the co-pending application. l s

The description will be made clearer with reference to the accompanying drawings which illustrate one practical embodiment of the invention, and in which:

Figure 1 illustrates a master timer from which separatepai rs of conductors radiate to dependent controllers.

Figure 2 illustrates one type of controller for a dependent intersection, regulated by impulses transmitted from the master timer.

Figure 3 is a wiring diagram for a type of right of way controller whose operation is dependent upon actuation of vehicle actuatable detectors in the several approaches to the intersection and upon pulsing from the master timer.

Figure 4 shows the modifications required in a right of way controller of the type shown in Figure 3, according to the present invention, for rendering such a controller suitable for use at a key intersection, and connections to the master timer operating in conjunction therewith.

-Fig'ures 5 and 6 are each sectional views of a conventional differential gearing arrangement,

utilized in a rotary stepping switch with dual stepping magnet and ratchet apparatus for producing movement of the wiper arms either clockwise or counterclockwise for use in the master timer. I

Figure 7 shows a modification of Figure 3 providing for master timer control impulses twice per cycle.

The system described in specification #403,732 relates to traffic control signals for use at road crossings or the like and ismore particularly concerned with a progressive type traificcontrol system bymeans of which a number of controllers located at successive intersections at a main road may be regulated from a master controller in a certain phase relationshipto each other, so that if the average speed of the trafiic is known it is possible to time the control signals so as to ensure a substantially continuous fiow of traffic along the main road.' The'arrangement moreover is particularly concerned'with systems in ;which the operation of the signals'may be controlled in accordance with the density of the traffic by the employment of vehicle detectors located in the roadway.

The system shown in Figs. 1 and 2 does not make use of vehicle detectors to regulate the timing of the signals but its operation will be described in order to permit a proper understand:- ing of the system illustrated in Fig. 3 in which vehicle detectors are employed.

It should be explained generally-that the system illustrated in Figs. 1 and 2 comprises a master. timer, from which separate pairs of conductors radiate to each controller for the-purpose of regulating their time periods in relation to each other The controllers in one embodiment may be conveniently arranged to operate at fixed time periods independent of the traffic flow, that is to say, there is no question of extending their normal period as a result of a continuous fiow of tiafiic passing over a road contact or the like. These controllers will be set to operate at rather long periods, considerably in excess of that required in the progressive system, but the periods will be curtailed by the right amount upon the reception of so-called light and heavypulses over the controlleads from the master timer.

Referring now to the circuit shown, the system is arranged for operation from A. C. mains and suitable rectifying arrangements are provided for obtaining direct current to operate the relays and neon lamps. In the drawings the alternating current mains designated l0 and II are shown incoming from the left hand side in Fig. 1 and for the operation of the master timer a tapping is made from these leads by way of the fuses FUS and main switches MNS to the primary' winding of the transformer XFR. This transformer is provided with three secondary windings two of which connect with the thermionic valve amplifier VLV which supplies direct current of the order of 400 volts to the terminals designated and in a circle, for the purpose of flashing the neon lamp N. The third winding on the secondary side of the transformer XFR connects with the full wave metal rectifier bridge MRA which supplies direct current of the order of 50 volts to the terminal points marked and in a square, for the purpose of operating the relay F and the ,drivingmagnet DSM; Essen- 'tially the master timer comprises a rotary stepof which may. be altered, by varying the setting of the resistance switch l2 connected in series with the condenser QB.

As regards the automatic stepping circuit it should be explained that when the neon lamp N flashes as the result of the charging of the condenser QB to the required voltage, relay Z is operatedin series therewith, thereby at armature zl operating relay F, and at armature 22 connecting negative potential to the wipers of the switch DST. Relay F on operating, at armature f2 completes the circuit. for the driving magnet DSM, at armature fl supplements the connection to the wipers of the switch DST, at armature f3 shunts the neon lamp N and relay Z asalso condenser QB, by way of resistance YB and at armature f4 flashes the master fail alarm lamp MFA. Relay Z thereupon releases and upon the release of relay F after its slow period due to the copper slug on its core, the driving magnet is de-energized to advance the wipers on to the next set of bank contacts. automatically so long as the system is in service. One bank and wiper of the switch DST is allotted to each controller to be regulated and the control leads extend, from the appropriate contacts in the associated bank. Bank la connects with controller No. 1 of which only the regulating relays shown in Fig. 2, and bank Saconnects with controller No; 3, which is not shown as it is assum to be identical with controller No. 2.

In the'drawing each control lead is shown as making two connections with its associated bank,

This action continues Cil one of which is direct and the other extends by way of a resistance. Consequently as. the switch rotates so-called light and heavy pulses are delivered over the control leads to the respective controllers in turn.

The control leads may comprise light gauge wires, for example telephone lines, and terminate in the controllers on a pair of relays B and 0 shown in Fig. 2 connected in series, one of which is marginal. or both of-these relays from the light and heavy pulses the signal lights of the controller are regulated accordingly.

In this particular example the complete cycle time of the system is represented by 25 steps of the rotary switch DST in the master timer. Each step of the switch therefore represents 4% of the total cycle time so that by varying the connection of the control leads to the banks the phase relationship between the different sets of control signals may be adjusted to a very fine degree.

Each of the controllers, which are all identical, comprises essentially a battery of cams mounted on a common shaft and arranged to close contact springs in a particular order. As regards the No. 2 controller shown in Fig. 2 it should be explained that the cam shaft is rotated step by step under the control of 'a solenoid S which is impulsed at predetermined time periods from a neon lamp timing device, comprising the lamp LN and impulse relay A together with condenser QA and charging resistance l3. The cam. assembly is moreover, a standard unit which may be used in different circumstances and controls 22 spring sets with six different positions. The full number of cams is not employed in the present instance and the chart shown in Fig. 2 shows the effect of the various cams which are used in this particular arrangement. The cam contacts which are operated in each of the six positions are designated in the chart by a black circle or bar.

If it is assumed with regard to controller No. 2 that the cam shaft is in its first position, cam contacts CI, C9 and C22 will be operated, thereby lighting the green signals lamps GNS for the north-south road, and the red signal lamps REW for the east-west road, while at the same time over cam contacts Cl, a circuit is complete from the valve rectifier -IVLV by way of a tapping on the common resistance l3 for charging the condenser QA. After the initial period of for example 10 seconds has elapsed, the condenser'QA will be charged suiliciently to cause the neon lamp IN to flash over, thereby operating relay A which at armature al energizes the solenoid S which advances the camshaft into its second position. In this position, as will be evident from the chart, the signal lamps already lit are maintained and over cam springs C2 and the adjusting switch shown a charging circuit is again completed for the condenser. Four such adjusting switches are shown in the drawings and it should be explained that the terminals of these switches connect with suitable tapping points on the common resistance l3. To meet the require-.

ments of the invention the resistance now connected in circuit .must be very' high to ensure that the condenser charges slowly, and for this reason the adjusting switch in question is preferably turned roun'd into its extreme position where it will beunderstood that it connects with the end of the common resistance shown.

During progressive working this particular As a result of the operation of onev timing circuit will have practically no effect on the operation of the controller since with the normal operation of the master timer a light,

pulse is delivered over the control leads before it becomes operative to charge s'ufllciently condenser QA As already explained this light pulse is obtained by including a high resistance in the pulse leads at the banks of the master timer, and as a result relay B only is operated in the controller, thereupon at its armature bl in conjunction with the cam contacts Cl8 completing a low resistance charging circuit for the condenser QA. Almost immediately therefore the neon lamp IN flashes and causes the controller to step to position 3. Non-inductive resistances are connected across the control leads as shown in order to guard against false operation owing to surges and inductive discharges.

In accordance with the change of the cam contacts, the green lights for the north-south road are now replaced with amber lights ANS, and over cam contacts C3 and the adjustable resistance switch a circuit is completed for the condenser QA to control the duration of the amber signal. With this arrangement although the phase of the amber signal may be changed when an adjustment is made in the cycle at the master timer, its actual duration remains constant since it is determined by the setting of the local adjusting switches and is not influenced by the relays connected to the control leads.

In case it should be desired to show the amber signal simultaneously to both roads, as is the requirement of certain administrations, this may be achieved by bridging the amber circuits by means of the switch I4 shown in the drawings,

- After the duration of the amber warning period the solenoid S again operates to step the cam shaft to position 4 and the control signals are then completely reversed while over cam springs C4 'a charging circuit is completed for the condenser QA- which provides an initial timing period of 10 seconds for the east-west road. When this period has elapsed, the solenoid S steps the cam shaft to position 5 and although the signals previously showing are retained, the charging circuit for the condenser QA is completed by way of the very high-resistance as a result, of the adjusting switch associated with cam contacts C5 being turned into an extreme position.

Here again this second comparatively long time period has practically no effect upon the controller during normal progressive operation since a heavy pulse will be received from the master timer meanwhile, which results in the operation of both relays B and C, and the latter at armature cl in conjunction with the cam contacts C7 steps the cam shaft into its final position 6. In this manner the controllers are stepped progressively depending on the connections to the banks of the timing switch, and providing the master timer is functioning correctly,

the time periods of their stop and go sig-' nals will be directly regulated therefrom.

If however for any reason the master timer should fail in such a manner that no further impulses are delivered over the control leads,

trol conductors should maintain operated one 2 or both of the signal relays at the controller,

4- p the latter will continue to function at somewhat shorter time intervals as determined by the initial timing-circuit completed over cam contacts Cl and C4.

In addition to the normal operation of the system and the necessary safeguard against failure. it is also possible to provide special features such as for example causing all controllers to show a. red signal to all approaches thereby effecting a compete hold up of the traflic. Thisis provided which is located in a conspicuous position at the master timer and arranged to flash in synchronism with the stepping switch. Any abnormal condition such as the blowing of the main fuse or failure of the neon lamp will be indicated by the failure of the supervisory lamp to light. v s

In case the masteratimer is switched on at a time when certainof the controllers are out of phase, the correct phase setting between each will be restored when the stepping switch in the disconnects the operating circuit for the com troller which is thus brought to rest in the position to which it is set, at armature ar2 opens the circuit ofv the green and amber signal lampsand at armature 'ar3 bridges the circuit of the red signal lamps so that both sets are lighted. It will be appreciated from a consideration of the chart that in all positions of the controller one or other of the red signals will be showing and therefore, the connection described will be effective no matter in what position the con troller is brought to rest.

For the purpose of switching the controllers on and off a further common wire I6 is provided which connects with the switch contact CSS3 at the master point and ,a relay CS in each controller. The operation of the manual switch to a second position disconnects the master timer insofar as its control functionis concerned by opening the circuit to the valve recti- 'fier VLV at springs CSSI and cssz, and at springs CSS3 connects potential to thecommon' lead IE to operate a relay CS in all controllers, which thereupon at armatures csi disconnect the respective controllers from the alternating currentmains. This method of control is preferred to the alternative, whereby the relay is operated to connect up the controller since a failure are not closed. In these circumstances the mas ual key is operated, the springs ARSI and ARS2 i are actuated. thereby disconnecting the circuit for'the green and amber signal lamps and also connecting together the red signal lamps so that both sets show simultaneously regardless of the position of the controller.

In case it should become necessary under certain circumstances for a particular controller to be operated manually, the required circuit changes are brought about by the operation of a I .further key which actuaitesv the springs MANI and MAN! to disconnect the timing circuit of the 'controller and also connects thesolenoid S in circuit with a pushbutton PB. The operation of the push button by the ofilcer'in charge causes the controller to step through its cycle and any I desired time periods may be allowed.

As already enplaineda supervisory lamp MFA 'circle and a square.

master timer has made one complete revolution.

Considering now the arrangement of another embodiment of the controller illustrated in Fi ure 3,'this represents the equipment at an individual-controller whichis intended to perform similar functions to that illustrated in Fig. 2. It will be appreciated however that the current supply arrangements are shown somewhat diflerently and also that relays such as CS, AR and C will still be required t6 respond to signals from the mastercontroller which in this case need send only one control impulse per cycle which operates relay C. The controller of Fig. 3 is of the same mechanical construction as that illustrated in Fig. 2, that is to say, it is providedwith' a number of sets of contacts operated by a cam shaft which is moved step by step by means of a solenoid. Moreover, the stepping of the solenoid .is again controlled from a timing circuit employployed and two road relays are provided which respond to the passage of vehicles over'the detectors. In view of the description which has already been given it will not be necessary to describe in considerable detail the working of the apparatus illustrated in Fig. 3 but the more salient features of operation will be considered briefly.

The current supply is assumed to be taken from alternating current mains and is rectified to provide direct current for the operation of the neon lamps. The transformer XFR feeds the valve rectifier VR. and also supplies alternating current of a suitably reduced voltage for the operation of the road relays. The live pole of the A. C.

circuits is represented by a plus in a circle, the

live pole of the D. C. circuits by a plus in a square and the common earthed pole ,by a minus in a The chart shows as before the positions 'of the cam shaft in which the various cam contacts are closed. The various interval adjusting switches INS, VNS, IEW, VEW, LNS, LEW are wired to appropriate tapping points of the resistance 20, and similarly the switches MNS and MEW are wired to resistance 2! which gives tappings of higher value.

For convenience of. description it will be assumed first of all that the cam shaft is standing in position 6 giving right of way to the street NS and that there is no traffic on either street. In'these circumstances a charging circuit is completed over contacts 04 and, the adjusting switch VNS for the condenser QJ, but owing to the fact that neither relay D nor relay E is operated in the absence 'of trafflc assumed and the consequent absence of closure of road contacts DEW and DNS, and with contact (12 therefore open, it is impossible for discharge to. take place through the neon lamp FJ when the condenser becomes charged to the striking voltage since cam contacts Cl! and C" are open in this posi- 7:.

.K cannot be operated even though the armature c! be operated due to the receipt of a pulse from the master timer, so that solenoid S cannot be operated and the cam shaft will remain in this position.

Suppose now that a vehicle'arrives on the road EW, relay D will be energized due to theoperatlon of a trafiic detector DEW and since contacts C6 are closed, a circuit is completed over armature d2 for striking lamp FJ so that relay J is enersized and the solenoid-is, operated at armature ii and the cam shaft'is moved to position I. In this position the lamp ANS is lighted in place of GNS and lamp. AEW is lighted in addition to lamp REW if the switch connection is used. Moreover, a new charging circuit is completed for condenser QJ over cam contacts Cl3, the adjusting switchLNS and the appropriate charging resistance. Relay D moreover was locked up overarmature di and contacts C! so that as soon as the condenser QJ has been charged sumciently which will occur after a few seconds only, relay J is again operated and advances the cam shaft to position}. In this position lamps GEW and RNS only are lighted and the vehicle in the street EW secures right of way. Furthermore a new charging circuit is now completed for condenser 'QJ, this time over contact CM and switch IEW. Consequently, after the period corresponding to the resistance now included in the charging circuit relay J is again operated and the solenoid steps the cam shaft to position 3. This produces no change in the lights but the charging circuit for condenser QJ now ex-, tends over contact CIS and the switch VEW. Moreover, relay D isde-energized by the opening of contacts C1 and owing to the closure of contact CIB a circuit is prepared for shunting condenser QJ via relay contact d2. If there is no furthertraflic, relay D will remain deenergized and contact d2 will remain open so that the condenser QJ will become fully charged, but until relay E for the N-.-S road is operated the contact e2 will be open and since also cam con-- tact C6 is open in this position 3, relay J cannot be operated and condenser QK cannot be charged so that neither relay J nor relay K is operatedand the cam shaft remains in position 73 with right of wayon the E--W road.

If further vehicles arrive on the EW road however relay D is again operated and shunts the c'o'ndenser by way of the comparatively low resistance YE and contact d2 and thus extends the time which will be required for the condenser to be; charged to the'striking voltage of the lamp, FJ. It may be pointed out that since in these circumstances relay D is only operated while the ve cle is actually passing overthe detector pad, the amount of extension obtained is dependent on the speed of the vehicle, being greater. for a slow moving vehicle than for afast moving one.

If now a vehicle should arrive on the road 'NS, relay E will be operated and contacts CIT charging of condenser QJ.

1 in turn in the manner previously described but by successively charging condenser QA over adjusting switches LEW and INS to giveright of way to. the road NS. I

In case, however, the traflic on the road EW should be substantially continuous, that is to say, there should be no break in traflic flow sufliciently long to permit condenser QJ to charge up, the maximum timing circuit involving the condenser QK comes into operation. It will be noted that this circuit comes into operation as soon as there is a waiting vehicle on the road NS at which time relay E is operated and locks up over contacts Cl8. The charging circuit for condenser QK now extends over contacts CH! and theswitch MEW by means of which a resistance is connected in circuit which will permit the condenser QK to charge up only after an. interval considerably greater than that required for the the fact that cam contacts C8 are only opened,

in position 6 that'ifthere should be a continuous stream of trafiic coming from the road EW, that is the side road, the main road will receive right of way as soon as the condenser QK becomes sumciently charged because relay K which also operates the solenoid S over armature lcl has its operating circuit completed over contacts C8 in position 3 of the cam shaft. In the case, however, of continuous traffic on the main-= road, that is NS, with traflic waiting on the side road EW,

even though the condenser QK becomes sumciently charged it is impossible for it to discharge through relay K and neon lamp FK until the instant at which a' pulse is received from the master timer to energize the master control relay a (corresponding to relay C in Fig. 2) and operate armature c'l. Accordingly if the traflic on the main road is substantially continuous so that the several individual controllers are working on their maximum periods, the actual instants at which the several controllers withdraw right of way from the main road are controlled by the master controller thru relay C and contact c'l in each individual controller. Because the time sequence of operation of the several relays C ,(C, in Fig. 2) is determined by the mastertimer, as explained in connectionwith Figs. 1 and 2, thetime when each relay C' permi ts its associated controller to withdraw right of way from the main road thus may be adjusted at successive intersections along a main road to permit main road traflic to proceed with the minimum delay.

It will be noted that armatures d3 and c3 when' operated serve to include resistances YF and YG in their respective amber timing circuits so that when right of way is being forcibly removed thus intercepting a stream of trafiic an' additional amber period is given to facilitate clearing the crossing. Similar control may be obtained by means or the amber extension switches ENS, EEW.

The switches PNS and PEW are so-called arterial switches and when operated ensure that right of way shall return to the associated street in the absence of traflic thereon. Their efiect is to simulate the operation of the pads at a time when'the street in question is not receiving right of way by energizing the respective relays E and D in cooperation with cam contacts CH3 and C1 respectively in all positions except 6 and 3 respectively, though they do not produce any extension effect when the street already has right of way unless the respective pads are operated.

The solenoid S is provided with three sets of contact springs of which slv and s2 serve to shunt condensers QJ and QK by low resistances YJ .and YK respectively. Springs s3 are effective in conjunction with armature 102 to ensure that without any further operation of the associated detector right of wayshall be returned to the street from which it has been forcibly removed.

It will be understood that the master timer and associated control relays are operated con-. tinuously so that relay C in each individual controller is operated once each cycle. This operation only produces any eifect however if the trailic on the main road is so heavy as to run the controllers up to their maximum timing periods.

An embodiment of the invention will now be described in which a'right ofway controller of the type shown in Figure 3, having detectors in the several lanes of approach to the intersection, and with the modifications which will' magnet DSM energized periodically by impulses whichin this embodiment of the invention originate from a condenser-flasher tube arrangement, similar in all respects to that shown in Figure 1. As mentioned above, the local dependent controllers, for all intersections of the group except the key intersection which is vehicle actuated, may be of the same form as the controller of Figure 2, in which impulses from the master timer control the time when right of way isaccorded tothe main traiilc lane and the crosslane.

Referring now to Figure 4, there are reproduced herein portions of Figure 3 inwhich modiflcation or addition is-required for the use of such a controller at a key intersection according to the invention the balance of Fig. 3 representing principally the road relays D and E and road contacts DEW and DNS, as well as the signal cams and circuits it will be understood are assumed to be a part of Fig. 4. Further only a portion of the master timer of Fig. 1, including modification, has been reproduced in the left hand'portion of Fig. 4'. The timing circuits of the key controller are now connected to ground from terminal 56 either over back contacts of a relay G or front contacts of a relay H instead of directly to ground as in Fig. 3. Relay G is energized by the'closure of an added pair of cam contacts C23. during the main road vehicle interval (shaft position 6), and this breaks the timing circuit to ground at gl unt'il relay H is energized. A circuit to energize the relay H is completed by armature rl when the latter is attracted by relay R which is energized in a certain position or positions of the master timer DST by its'wiper l3. Relay H may be locked in during the main street vehicle interval over cam contacts C24. It will be understood that the relay B may be placed with the key controller instead of with the master timer as shown in Figure 4, if desired, the circuits remaining the same as in Figure 4.

A circuitover armature 12, when relay R is energized, is completed over armature g2, either to timing increase magnet INM, or to timing decrease magnet'DEM of a double-acting rotary switch DDT, depending upon whether 92 be engaging contact 30 or contact 3| it will be appreciated that relay R may be located with the key controller if desired, in case the latter is remote from the master timer.

The rotary stepping switch DDT is of a type provided with two stepping mechanismsso connected that the wiper arm 12 may be operated over its contact bank in either direction. For this purpose magnet DEM is arranged to. notch in one direction the ratchet wheel 25, Figures 5 and 6, mounted on shaft 26, and magnet INM'is similarly fixed to notch ratchet wheel 21, on the shaft 28, in the opposite direction of rotation to shaft 26. The differential gearing permits member 29 to revolve in either direction, depending upon whether shaft 26 or 28* is rotated. Wiper I2 is mounted on member 29 and is suitably shaped to revolve over its associated bank of contacts of the switch DDT either clockwise or counterclockwise.

'Againreferring to Figure 4, the contacts of switch -DDT are connected to points which may preferably be equidistant on rheostat 22, which stands in the condenser QB'l and flasher tube N impulsingcircuit of magnet DSM of .the master timer stepping switch DST.

Assume now that the solenoid of the key controller steps its camshaft into shaft position 6, the A phase or main street vehicle interval position. Cam contacts C23 are closed energizing relay'G. Thus at armature GI the direct current feed for the A phase vehicle interval and maximum timing circuits become disconnected from ground, thereby stopping all timing. A particular contact on the bank la of the rotary switch DSTin the master timer is selected in accordance with the predetermined progressive plan for operating the dependent controllersso that the wiper l3 comes into engagement with this contact at the same time as the cam contacts C23 close, whenthe master timer and the v key'controller are operating on the same length cycle.

When the master timer and the key controller, due to trafllc conditions affecting the latter, are not operated in the same length cycle and if the master timer is operating on a longer cycle than the key controller, relay R, which is connected to the synchronizing contact of bank la, will be energized after relay G, and when relay R has attracted armature rl, relay H is energized and locked in over its armature hl and cam contacts C24. This pair of contacts is closed only during the phase A vehicle interval, shaft position #6. Relay R at armature rz completes a circuit over armature 92 to energize decrease magnet DEM of double acting rotary switch DDT. Accordingly magnet DEM causes wiper arm 12 to be stepped clockwise one contact, thereby reducing the amount of resistance 22 in the charging circuit of condenser QB. The frequency of impulses fromthe' impuising circuit to magnet DSM of the master timer is thus increased and consequently the time for one cycle of the master timer is decreased. v

In the circumstances described, since relay R has operated after relay G, when the master to v timer is operating on a longer cycle, the decrease 75 fore rela'y G, which sequence occurs when the master timer is operating on a shorter length cyclethan the key controller, the increase magnet INM is energized, wiper ari'n I2 is stepped counterclockwise one contact, thereby increasing the resistance 22 in the impulse-generating circuit, and the master cycle time is increased say by 4%. As already explained, relay R upon being energized, pullsin relay H which locks-in at armature hi, and at armature h2 reconnects the direct current feed for the timing circuits to ground, whereupon the key controller recommences normal timing; the condensers Q1 and QK begintocharge and upon operation of relay J or K the cam shaft is advanced into position I.

When the cam shaft is stepped into the amber leaving phase A position the cam contacts C23 and C24 open, relays G and H drop out and the key controller and master timer operate thru their next cycle independently.

It will thus be seen that successive energizae tions of relay G are raced against successive energizations of relay R. If the cycle time of the key controller is longer than that of the master timer, in which case relay R is energized before relay G, the next cycle of the master timer is lengthened; if the cycle of the key controller is shorter than that of the master timer, in which case relay R is energized after relay G, the key controller timing is interrupted until the master timer completes its cycle, and the next cycle of the latter is decreased.

In lieu of the arrangement just described in which the armatures gl and ht are inserted in parallel-between terminal 56 and ground, itwill be obvious to those versed in the art that in an alternative arrangement terminal 55 may be connected to ground and the armatures gl and hi placed in parallel between terminals 55 (or in the case of the key controller by an armature 13 in the master timer for example, as shown in Figure 4, or the cam contacts C8 may be shunted altogether, since the arrangement to stop timing in the key controller in position 6 when this controller completes its cycle before the master timer holds the two machines closely in step, and renders other coordinating means unnecessary.

It will. be appreciated that dependent local controllers of the type shown in Figure 2 and operated from the master timer according to the method shown in Figure. 1 and thereinabove described may be replaced by full vehicle actuated right of way controllers of the type shown in Figure 3, or theymay be replaced by conwhich impulses from the master timer are sent ,trollers having vehicle detectors in the side roads only withthe vehicle detectors circuit on the main road via DNS preferably permanently closed. In the latter case a system of control from the master timer becomes established in over control leads to relay C'in the dependent controller in the same fashion as to relay C in Fig. 1 and Fig. 2, and such impulses from the master timer will indicate when right of way may be removed from the main road if the side road detector has been operated. The master timer would in this case however be set to give the impulse to relay C at the point in its cycle at which it is desired to have transfer of right of .way from the main road NS to the side road EW occur at the local controller.

In addition if desired a second impulse operating a relay B, in similar fashion to relay B in Fig.1 and Fig.2 for example, may indicate when right of way must return to the main road, if right of way has been retained on the side road by continuous traffic. Fig. 7 showshow Fig. 3

, may be modified in accordance with the arrangements of Fig. l and Fig. 2 to provide two such controlimpulses per cycle of the master timer, the armature c'l cooperating with cam contact C'8 in position 8 to control transfer of right of way from NS and armature b'l cooperating with cam contact B'l9 in position 3 to control transfer of right of way from EW by the master timing circuit. With these alternative arrangements if there is no trafiic on the side road, right of way will remain continuously on the main road. Also right of way will return to the main road after being accorded to the side road if all the sideroad trafilc has passed so that condenser QJ is charged and tube FJ operatesibefore the second impulse is received.

Thus the several objects specifically brought out above, and others are achieved. It isto be understood that various modifications in the structural details or arrangements of the parts, orchanges' in the designs herein exemplified may be made without departing from the spirit of the invention as defined by the claims.

4 Having described my invention what I claim as new 'and desire to secure by Letters Patent of the United States is:

1. In a traffic control system for a plurality of intersections of interfering trafiic lanes, the combination of means for according right of way through a cycle to the several lanes at one intersection, a second'means at another intersection and adapted to be actuated by traffic for according right of way through a cycle to the several lanes atthe latter intersection variable in ac- (ordance with traffic actuations in said several.

lanes, means for increasing the cycle of the first means, means for decreasing the cycle of the first means, and selective means responsive to the order of completion of the cycles of the first and second means for selecting between said means for increasing or decreasing the cycle of said first cycle increasing and cycle decreasing means.

2. In a trafiic signal control system for a plurality of intersections of interfering traflic lanes, the combination of right of way signals at the several intersections, a primary right of way signal controller at one intersection and traffic actuatable devices in the lanes thereat, said controller operable in response to actuation of said traflic actuatable devices in the respective lanes at said on'eintersection to accord right of way cyclically to the several lanes thereat in succes-.

sion for variable periods of time in accordance with said actuations, a secondary controller for controlling the signals at another intersection through a cycle of right of way indications, means for altering the length of the cycle of said secondary controller, means operable responsive to the order of completion of the cycles of the primary and secondary controllers for operating said first named means.

3. In a traiiic signal control systemifor a plurality of intersections the combination of 'right of way signal indicators at each intersection, a

primary signalcontroller at one intersection and tramcactuatable devices in the lanes thereat, said controller operable in response to actuation of said frame actuatable devices in the respective lanes at said one intersection for according right of way cyclically to the several lanes thereat in succession for variable periods in accord.-

ance with said actuations, a. secondary signal controller for operating the signals at another intersection through a cycle of right of way in- 4. In a trafiic control system for a plurality oflntersections of interfering traffic lanes, the'combination of right of way signals displayable at the several intersections, a. key right of way controller at one oi the intersections and trafficactuatable devices in the lanes thereat, said controller operable in response to actuation of said devices in the several lanes at said one intersection for accord-' ing right of way cyclically to the several lanes in succession for variable periods in accordance with said actuations, a master timer for cyclically controlling the display of such signals to the several lanes at a second of said intersections, means associated with said master timer for altering the length of the next cycle of. the master timer to approach the duration of the last completed cycle of the said key controller,.and further means operating when the master timer has reached the end of its cycle for making saidi'flrst means operable for such next cycle.

5. In a traiiic control system fora plurality of intersections of interfering trafiic lanes, the combination of right of way signals displayable at the several intersections, a key right of way controller at one of the intersections and trailic actuatable devices in the lanes thereat, said controller operable in response to actuation of said devices in the several lanes at said one intersection for according right of way cyclically to the several lanes in succession for variable periods in accordance with saidactua'tions, a master timer for cyclically controlling the cisplay of such signals to the several lanes at a second of said intersections, means associated with said-master timer for altering the length of the next cycle of the master timer to approach the duration of the last completed cycle of the said key controller. and further means operating when the key controller completes its cycle before the master timer completes its cycle for stopping said controller at the end of the cycle of the rightof way controller until the master timer has comletedits cycle.

6. In a trafllc control system for a plurality of intersections of interfering traific lane's, the combination of right of way signals at the several intersections, a cyclic master timer comprising a periodic electrical impulse generator and a switching mechanism which is stepped thru a 3 cycle in steps by and corresponding to said impulses for operating said signals at one of said intersections thru a cycle of rightoi way indications, a key controller at another intersection I and traiilc actuable devices located in the several lanes thereat, said controller operable in response to actuation of said devices in the respective lanes at said latter intersection for successively according. right of way cyclically thru said signals to the several lanes for variable periods in accordance with said actuations, means associated with the master timer for altering the lengthof its cycle toward thelength of the cycle of said key controller, and means operating at the end of each cycle of the master timer for operating said firstmeans.

7. In a trailic control system for a plurality of intersections of interfering tramc lanes, the

combination of a cyclic master timer comprising a condenser, means for producing a charge 'on said condenser varying over a time period to a certain value, means including a flasher tube connected to said condenser and operable only when the charge on said condenser reaches said certain value to generate an impulse, and a cyclic switching device which is, stepped thru its cycle in steps by and corresponding to said impulses,-

right of way signals at one of the intersections and controlled cyclically by said master timer, a right of way controller at another intersection and tramc actuatable devices located at the several lanes thereat, said controller being operable in response to actuation of said devices'at said.latter intersection for successively according right of way cyclically tothe several lanes for variable periods in accordance with said actuations, a variable resistance in said charge varying means for altering the frequency of said impulses to the master timer by varying the time rate of variation of charge of the condenser, and v means for automatically varying said resistance for altering the cycle length of the master timer toward the length of the cycle of said right of way controller, in accordance with the order of completion of the cycles of said master timer and said controller.

8. In a trafllc control system for a plurality of intersections of interfering trafiic lanes, the combination of right of waysignals at each intersection, a key controller and traffic actuated devices in the lanes at one intersection and connected to said controller for controlling the signals thereat, said controller being operable in response to actuation of said tramc actuatable devices at one intersection for according right of wayto the several lanes in succession in a cycle for variable periods in accordance with the said actuations, a master timer for operating the signals at another intersection through a cycle of right of way indications, means associated with the master timer for increasing its cycle and means operable upon the master timer reaching the end of its cycle before the key controller has completed its cycle to make said first means operable.

9. In a traflic control system for a plurality of intersections of interfering tramc lanes, the

combination of right of way signals at each in-' tersection, a key controller and tratflc actuated devices in the lanes atone intersection and connected to said controller forcontrolling the signals thereat, said controller being operable in response to actuation of said traffic actuatable devices at one intersection for according right of way to the several lanes in succession in a cycle for variable periods in accordance with the said actuations, a master timer for operating the signals at another intersection through a cycle of right of way indications, means associated with the 15 master timer for decreasing its cycle and means operable upon the master timer reaching theiend of its cycle after the key controller has completed its cycle to make said first means operative.

10. In a traffic control system for a plurality of intersections of interfering trafiic lanes, the combination of right of way signals at each intersection, a key controller and traflic actuatable de vices in the lanes at one intersection and connected to said controller for controlling the signals thereat, said controller being operable in response to actuation of said trafl'lc actuatable devices at said one intersection for according right of way to the several lanes in succession in a ,cycle for variable periods in accordance with the said actuations, a master timer for operating the signals at another'intersection through a cycle of right of way indications, means associated with the master timer for decreasing its cycle, and means operable upon the key controller completing its cycle before the master timer to stop said v key controller until the master timer has completed its cycle, whereupon said first means is rendered operative.

11. In a traffic control system for a plurality of intesections of interfering trafilc lanes, the

. combination of right of way signals at each in right of way indications, means including a cir-,

cult andoperable when said circuit is completed to shorten the cycle of said master timer, means operable upon the key controller completing its cycle before the master timer has completed its cycle for stopping said key controller and for preparing said circuit to shorten the next succeeding cycle of said master timer, and means operable when the master timer thereafter completes its cycle for restarting said key controller and for completing the circuit prepared by said first means.

12. A trafiic. control system for a plurality of intersections oi interfering trafllc lanes including in combination an; electrical periodic impulse generator, acyclic rotary electric switching device which is stepped through its cycle in steps by and corresponding to said impulses, right of way controlling means at one intersection and controlled by said rotary switching device, a key right ohway'cdntroller and tramc actuatable devices in the lanes at another intersection and connected to said controller, said controller being operable responsive to actuation of said trafiic actuatable devices at said latter intersection for according right of way tothe several lanes in succession in a cycle for variable periods of time in accordance with said actuations, means associated with said impulse generator for increasing the frequency of its stepping impulses and means co-operablev upon ,the said rotary switching device completing its cycle after the key controller has completed its cycle to make said first means operative;

13. A tramc control system for a plurality oi intersections of interfering tramc lanes including in combination an electrical periodic impulse generator, a cyclic rotary electric switching comprising an electrical periodic impulse which is stepped through its cycle in steps by and corresponding to said impulses, right of way controlling means at one intersection and controlled by said rotary switching device, a key right of way controller and trafilc actuatable devices in the lanesat another intersection and connected to said controller, said controller being operable responsive to actuation of said traflic actuatable devices at said latter intersection for according right of way to the several lanes in succession in a cycle for variable periods of time in accordance with said actuations, means associated with the said impulse generator fordecreasing the frequency of its stepping impulses and meansscooperable upon the said rotary switching device completing its cycle before the key controller has completed its cycle to make said first means operative.

14. A trafflc control system for a series'of intersections of cross traillc lanes with a common main lane including, in combination, right of way signals at each intersection, an electrical periodic impulse generator, a rotary electric switching device which is operated by said impulses to control said signals through a cycle of right of way indica- 25 tions with a progressive time phase displacement of such indications at successive intersections, a key right of way controller and traffic actuatable devices in the lanes at one intersection and connected to said controller, said controller being operable responsive to actuation of said trafflc actuatable devices at said latter intersection, for according right oilway to the several lanes in succession in a cycle for variable periods of time in accordance withsaid actuations, means associated with said impulse generator for altering the frequency of stepping impulses to the switching device to lengthen or shorten its cycle toappreach the duration of the last completed cycle of said right of way controller; and further means operable whenthe said switching device has completed'a cycle for making said first means effective.

15. A traffic control system for a series of intersections of cross trams lanes with a common main lane, including, in combination, right of way controllers at each intersection, a key right of way controller and trafliqactuatable devices in the lanes at one intersection and connected to said controller, said controller being operable in response to actuation of trafllc actuatable devices in the approaches to said intersection for according right of wayto the several lanes in succession in a cycle for variable periods 01 time in accordance with said actuations, a master timer generatgr and a re .electric switching device opera tiid cyclically byv said impulse for operating the indications of the othercontrollers with a progressive time phase displacementat successive intersections, means" including a resistance for regulating the time spacing of said impulses,.

means for altering said resistance to lengthen ,or. shorten the cycle of the master timer toward the length 01' the cycle of said key right of way controller, and further means operable when the said switching device has completed a cycle to make said first means active.

16. A tramc signal controlsystem fora series of intersections, of cross traiilc lanes with {70 common main lane including, in combination, a

key right of way controller, tramc actuatable devices in the lanes at one intersection and connected to said controller, said controller being operable-in response to actuation of said tramc actuatable devices at said one intersection for according right of wayto the several lanes in succession in a cycle for variable periods in accordance with said actuations, a right of way controller and a 5 trafllc actuatable device in the cross lane at another intersection andconnected to said latter controller, said controller operable in response to actuation of said trafilc actuatable device in the cross lane to accord right of way to such cross lane, a cyclic master timer for controlling the ability of said latter controller to respond to actuation of its associated actuatable device to maintain the accord of right of way at the intersections in predetermined time relation, and means for altering the length of the cycle of said timer in accordance with the length of the cycle of said key controller, and means functioning when the master timer has completed a cycle for making said first means operable.- 1'7. In a traiiic control system for two intersections of interfering traflic lanes including, in combination, right of way signals at each intersection, mechanism for controlling the signals at one intersection comprising a condenser, means 26 for producing a charge on said condenser varymg over a time period to a certain value, means including a flasher tube operable only when saidcharge on said condenser reaches said certain value-for generating a momentary impulse, and 80 a rotary switching device which isv stepped thru a cycle in steps by and corresponding to saidimpulses for operating said signals thru a cycle of signal indications; a key controller at the other intersection for controlling the right of way sig- 35 nals to the several lanes thereat, and traflic actuatable devices in the last said lanes and connected to said controller, said controller being operable in response to actuation of said trafllc actuatable devices at said latter intersection for according right of way thru said signals tothe several lanes in succession in a cycle for variable periods of time in accordance with actuations; a variable resistance in said charge varying means for adjusting the time rate of variation of charge, and control means for increasing said resistance when said switching device completes its cycle before said key controller.

18. In a trafiic control system for two intersections of interfering traflic lanes including, in combination, right of way signals at each intersection, mechanism for controlling the signals at one intersection comprising-a condenser, means for producing a charge on said condenser varying over a time period to a certain value, means including a flasher tube operable only when said charge on said condenser reaches said certain value for generating a momentary impulse, anda rotary switchingdevice which is stepped thru a cycle in steps by and corresponding to said impulses for operating said signals thru a cycle of signalindications; a key controller at the other intersection for controlling the right of way signals to the several lanes thereat, and traffic actuatable devices in the last said lanes and connected to said controller, said ,cont'roller being operable in response to actuation of said traflic actuatable desaid switching device, completes its cycle after said key controller, and further-means operable upon said switching device so completing its cycle to make said control means operate.

AIJ'RED PERCY "BAILEY RENSHAW. 

